PulmCrit- Montreal Hospitalist & Resuscitationist Conference FOAMed

I recently got back from the inaugural Hospitalist & Resuscitationist conference, a fantastic FOAMy conference in Montreal organized by Phillipe Rola (@ThinkingCC). It was inspiring to participate alongside fantastic folks including Rory Speigel (@EMNerd), Jon-Emile Kenny (@heart_lung), Kylie Baker (@kyliebaker88), Lawrence Lynn(@PatientStormDoc), Andre Denault, and Segun Olusanya (@iceman_ex). Screencasts of my talks, audio clips, some videos from the conference, and some bonus rants are below. Jon-Emile has posted screencasts of his talks here, you should check them out as well. Vive le FOAM.

keynote lecture by Lawrence Lynn: Redefining sepsis

This is a truly epic lecture about using artificial intelligence to diagnose sepsis (including different subtypes of illness). It makes current definitions of sepsis look like the children's toys.

resuscitationists in a van talking about ECMO

Phillipe was kind enough to drive a bunch of speakers from downtown Montreal to the conference in the morning. This is some unedited audio from the resuscitationist van, mostly featuring the Segun Olusanya talking about ECMO. In my defense, I was only partially caffeinated at that point in the morning.

time to stop using normal saline

related

microblog interlude: how much acidosis does four liters of saline cause?

My presentation about normal saline vs. LR included the slide shown above. I must admit that I didn't put a ton of thought into this calculation – I thought that it would be pointing out something somewhat obvious. However, on twitter some folks accused me of over-estimating the amount of acid and thereby fear-mongering. So I went back and re-evaluated the amount of acid in normal saline in a variety of ways.

#1: back-of-the-envelope estimation

Let's compare four liters of normal saline with the same sodium load in the form of LR. Before we get going, two assumptions need to be made:

Stewart's physiochemical model indicates that all strong ions have an equivalent impact on pH. This implies that the calcium and potassium in LR is interchangeable with an equivalent amount of sodium.

We will assume that the liver converts all of the sodium lactate into sodium bicarbonate.

Based on these assumptions:

One liter of normal saline contains 154 mEq of NaCl.

One liter of LR contains the equivalent of 137 mEq of Na, 109 mEq of chloride, and 28 mEq of bicarbonate.

Four liters of saline contains 616 mEq of sodium chloride. This contains the same amount of sodium that is present in 4.5 liters of LR (LR is hypotonic so a larger volume is required). This leaves us with the following comparison:

Now, we will assume that HCl would combine in equimolar quantities with sodium bicarbonate to generate NaCl and water. Based on this assumption, 4 liters of saline is equivalent to 4.5 liters of LR plus 126 mEq HCl (or 32 mEq base deficit for every liter of saline).

#2: more sophisticated model

Omron 2010 published a paper with a more complex Stewart model to predict the pH effects of various crystalloids. Based on their calculations, saline would induce an even larger base deficit (roughly 44 mEq per liter saline).

#3: clinical evidence

Scheingraber 1999 randomized 24 women undergoing gynecological surgery to recieve intraoperative saline versus LR. The average amount of fluid recieved was 6 liters. Patients in the LR group had stable pH status, whereas patients in the saline group experienced an average decrease in base excess from -0.4 mM to -6.7 mM. Based on the patients' average weight of 68 kg, this change in base excess correlates to an increase in the base deficit of ~180 mEq. This is equivalent to a base deficit of 30 mEq per liter, or 120 mEq for four liters (matching estimate #1 above).

bottom line?

The above data suggest that four liters of saline will induce a base deficit of at least 120 mEq. To provide some clinical context, this base deficit would drop the bicarbonate level from 24 mM to ~19 mM in a 70-kg person. This seems congruent with my experience of observing patients' electrolytes during large-volume saline resuscitation.

The original slide was correct: giving someone four liters of saline is equivalent to resuscitating the patient with LR and then giving them >100 mEq of HCl. That's a fair amount of hydrochloric acid. HCl is typically dispensed in a concentration of 200 mEq/L, so this is equivalent to a half-liter bottle of hydrochloric acid. Imagine giving this much acid to a patient with sepsis or DKA and severe metabolic acidosis – that would be obviously dangerous and completely inconceivable. However, that is exactly what we are doing physiologically when we perform large-volume saline resuscitation. We just don't think about it.

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thanks for posting these josh! your talks were awesome. i had a great time meeting everyone. keep up the awesome work.

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8 months ago

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Jens Michelsen

A quick question on the steroid-podcast by PulmCrit: It seems that the Annane studies had more favorable results even though they were of poorer quality. An important difference was that they included fludrocortisone whereas Corticus and Adrenal did not. Do you think that that may have influenced the results? Thank you all for a fantastic blog!

Thanks. I don’t think fludrocortisone is doing anything. See the bottom of this blog for more discussion of this: http://emcrit.org/pulmcrit/aprocchss/. That said, if you were to use fludrocortisone there wouldn’t be anything wrong with that.

great question! The concentration of calcium in LR is below the normal range, so LR itself should never be able to cause hypercalcemia. So I don’t think that LR would be dangerous in a patient with hypercalcemia. That said, normosol or plasmalyte would probably be preferable in that situation because they are balanced crystalloids without any calcium.